1. Technical Field
The present invention relates to a photoelectric sensor used for, for example, detecting the passage of a moving object through a target location or detecting a change in the orientation of an object. The present invention also relates to a method for aiding the operational checking of a photoelectric sensor.
2. Description of the Related Art
Examples of photoelectric sensors include a type (transmission type) that receives light emitted from a light-projecting unit and passed through an area for detecting an object to be detected (hereinafter referred to as a detection target), and a type (reflection type) that receives light emitted from a light-projecting unit and then reflected by a detection target. The sensors of both types convert a signal indicating an amount of received light, output from a light-receiving unit, into digital data and input the converted data (hereinafter referred to as “data on an amount of received light”) into a processing circuit that incorporates a microprocessor. Then, these sensors compare the value of the data on the amount of received light with a preset threshold to determine the presence or absence of a detection target. They subsequently output a detection signal indicating an ON-state if the presence of the detection target is detected.
Depending on the purpose of the use of each sensor, instead of comparing an amount of received light with a threshold, the sensor may perform the process of calculating the change or the moving average of amounts of received light and compare the value obtained from this process with a threshold.
To stably detect a detection target with a photoelectric sensor of any type, it is preferable to check how the measurement data to be compared with a threshold changes in accordance with object movement and then to set the threshold. However, if detection targets move at high speed, signals indicating the amount of received light and data obtained from such signals change very fast, and it is very difficult to check such changes.
To overcome such a drawback, some conventional photoelectric sensors are designed such that the maximum and minimum amounts of received light detected within a predetermined period of time are discerned and they are displayed side by side, enabling a user to check the degree of signal change resulting from the movement of a detection target (see, for example, Japanese Patent Application Laid-Open Nos. 2005-181343 and 2004-104612).